Livestock nutrition
Vitamin requirements of sheep and cattle during a dry season
Dave Jordan, DPI&F
Introduction
The important vitamins for survival and growth of grazing animals are either manufactured in the rumen by the rumen microbes, in the body from sunlight, or are stored in sufficient quantity in the liver or contained in adequate amounts in available feed.
Even under drought conditions, grazing animals almost never require expensive vitamin supplements or injections.
Vitamin A
Vitamin A itself does not occur in plants, but the substance carotene in green plant material is converted in an animal's body to vitamin A.
Green pasture (including a green pick), tree or shrub leaves (including mulga), hay with good green colour and yellow maize all contain sufficient carotene to allow the animal to produce enough vitamin A to top up the reserves stored in the liver.
These reserves are readily available for use by the animal, even during drought, and will compensate for any dietary inadequacy; supplementary vitamin A is not generally required.
Signs of vitamin A deficiency are night blindness, eye discharges and ill thrift.
For a vitamin A deficiency to occur, the diet would need to be completely devoid of green plant material for a considerable period of time.
As little as 28 g (1 oz) of green material per day will provide the animal's vitamin A requirements almost indefinitely. This can be obtained from any green plant material, including browse and shrubs.
Adult wethers or ewes and cattle can store sufficient vitamin A in the liver to provide for a period in excess of one year with no access to any green plant material (at all), including mulga and other fodder trees or browsed leaves.
There is no evidence available to indicate that sheep wholly or largely eating scrub require vitamin A supplementation.
One possible exception is rams and perhaps bulls required for breeding after some months on dry pasture containing no green material. The fertility of rams is seriously reduced after they have been without any green feed for 2-6 months. Rams that are to be used for breeding and that have not had access to any green feed or leaves for 2-6 months should be given 1,000,000 I.U. (International Units) of vitamin A, a minimum of 6-8 weeks before joining, if there is no green feed available at the time.
A second possible exception is lambs and calves weaned from drought-affected mothers with depleted liver stores. Lambs and weaners that have been reared without any access to green feed or tree leaves for 3-4 months should be supplemented with 500,000 I.U. of vitamin A from the cheapest source available; 350,000 I.U. is sufficient for lambs. These amounts will give a high degree of protection for the subsequent 6 months, improving survival, growth and wool production.
Where administration of vitamin A is necessary, use the cheapest form available.
There is no evidence available to show the superiority of injecting vitamin A over drenching with vitamin A. On the one hand injection gives quicker and slightly higher liver storage, while drenching results in similar levels fairly quickly.
Over the long term, neither method of administration has shown to have an advantage over the other in vitamin A storage or utilisation. For drenching purposes, oil base, emulsion, and water-soluble forms of vitamin A are equally effective.
It may be advisable to give vitamin A to sheep and cattle given high-energy diets with little green feed in feedlots if they have been brought in after 3 or 4 months on dry feed; the recommended dose is about 1 million I.U. for cattle and 100,000 I.U. for sheep.
The supplement will generally not be necessary if the animals have been brought in from green pasture because their requirements not met by feed will probably be provided from reserves in the liver.
Vitamin D
Animals manufacture their own vitamin D requirements from sunlight and fresh or dry feed. The body also stores sufficient vitamin D to overcome dietary deficiency for several months.
Supplementation of drought or feedlot rations is unnecessary. Vitamin D deficiencies only occur occasionally in the southern areas of Australia.
Vitamin E
Vitamin E is contained in green plant material, hay and grain; the concentration in grain decreases during storage.
There are currently no confirmed reports of vitamin E deficiency in cattle in Australia, and deficiencies in sheep are rare.
Vitamin B group
Newborn lambs and calves have some stores of the B complex vitamins in their tissues with further supply being obtained from milk.
An active microbial population in the rumen will then usually synthesise sufficient B vitamins to meet requirements.
Summary
Producers shouldn't feel pressured into injecting or spending money on vitamin supplements just to 'do something' for their stock or because someone suggests there could possibly be a deficiency.
Millions of sheep have survived long droughts without any vitamin supplementation or injection over many years.
During any drought, there are usually sufficient periods of short green pick or shrub or tree leaves eaten to provide adequate vitamins.
Acknowledgements
This information on vitamin requirements during drought was based on on-property sampling and research conducted during droughts at DPI&F's Charleville and Yeerongpilly research centres.
Information was also sourced from other State departments of agriculture and the Standing Committee on Agriculture publication 'Feeding Standards for Australian Livestock - Ruminants'.
Further information
For further information contact the DPI&F Call Centre on 13 25 23 (Queensland residents) or (07) 3404 6999 (non-Queensland residents) between 8 am and 6 pm weekdays, or or e-mail callweb@dpi.qld.gov.au
This DPI&F Note is also published on the DPI&F's PrimeNotes CD-ROM.
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
File No: SW0091 . Date created: February 2002 . Revised: February 2005
